Irish Distillers, the maker of Jameson whiskey, has become embroiled in a court battle with a Californian winemaker over allegations of trademark infringement.

Jameson is the pre-eminent Irish whiskey in the US, and Irish Distillers sells over 1 million cases of the stuff annually across the Atlantic.

Madison Vineyards is a small wine outfit in the Napa Valley, producing a range of reds and whites including an intriguingly-named tipple called Light Horse.

Madison recently started producing its wines under the name Jamieson Vineyards, and tried to register the name as a trademark, prompting a missive from Irish Distillers’ lawyers, who say the winery’s name is too similar to its whiskey brand. Madison is now asking a Californian court to declare that there is no similarity between them. Irish Distillers has been given extra time to respond to the case.